Metal-organic frameworks (MOFs) are an emerging class of porous molecular materials (see Moulton et al., Chem. Rev., 2001, 101, 1629; Evans et al., Acc. Chem. Res., 2002, 35, 511; Lan et al., Angew. Chem., Int. Ed., 2009, 48, 2334; Uemura et al., Chem. Soc. Rev., 2009, 38, 1228; Das et al., Angew. Chem., Int. Ed., 2011, 50, 10510; Wiers et al., J. Am. Chem. Soc., 2011, 133, 14522; Kreno et al., Chem. Rev., 2012, 112, 1105; Li et al., Chem. Rev., 2012, 112, 869; Furukawa et al., Science, 2013, 341; and Shustova et al., J. Am. Chem. Soc., 2013, 135, 13326) assembled from organic linkers and metal ions or metal cluster nodes. They find application in gas storage (e.g., hydrogen, carbon dioxide, and methane storage), molecule separation, and drug delivery. MOFs can also provide a highly tunable platform to engineer heterogeneous catalysts for chemical reactions, including asymmetric organic transformations and/or transformations that cannot be achieved with traditional porous inorganic materials. See Kesanli et al., Coord. Chem. Rev., 2003, 246, 305.
Some asymmetric MOF catalysts have been reported that can provide enantio-differentiation. See Ma et al., Chem. Soc. Rev., 2009, 38, 1248; Falkowski et al., Isr. J. Chem., 2012, 52, 591; and Yoon et al., Chem. Rev., 2012, 112, 1196. The first MOF catalyst with significant enantiomeric excesses (e.e.'s) contained the C2-symmetric 1,1′-bi-2-naphthol (BINOL). See Evans et al., J. Am. Chem. Soc., 2001, 123, 10395; and Wu et al., J. Am. Chem. Soc., 2005, 127, 8940. The postsynthetically-generated Ti-BINOLate moiety in the chiral MOF was responsible for high e.e.'s observed for diethylzinc additions to aromatic aldehydes. See Wu et al., J. Am. Chem. Soc., 2005, 127, 8940. Subsequently, a Mn-salen-based MOF was used for the asymmetric epoxidation of alkenes. See Cho et al., Chem. Commun. 2006, 2563. Since these reports, additional stereoselective MOF catalysts have been developed based on BINOL- and salen-based ligands. See Tanaka et al., Chem. Commun., 2008, 820; Ma et al., Nat. Chem., 2010, 2, 838; Song et al., J. Am. Chem. Soc., 2010, 132, 15390; Falkowski et al., Angew. Chem., Int. Ed., 2011, 50, 8674; Zheng et al., Chem. Sci., 2012, 3, 2623; and Shu et al., J. Am. Chem. Soc., 2012, 134, 8058.
However, there remains an ongoing need in the art for additional heterogeneous catalysts for asymmetric catalysis. In particular, there is an ongoing need for additional catalysts that employ other chiral ligands and that have good efficiency and enantioselectivity and/or that have good stability and recyclability. For example, there is an ongoing need for additional heterogeneous catalysts that can catalyze reactions at low catalyst loadings. Further, there is a need for additional heterogeneous catalysts to catalyze additional types of enantioselective reactions.